This invention relates to an alloy with constant modulus of elasticity (hereinafter referred to as "a CME alloy") which is used with, e.g., a precision instrument; and, more particularly, to a CME alloy which possesses characteristics whereby modulus of elasticity is constant, even within a high temperature range, having great mechanical strength.
The CME alloy has a CME characteristics whereby modulus of elasticity has a prominently small dependency on a temperature falling within a range peculiar to said alloy. The CME alloy is generally used with mechanical members whose modulus of elasticity should be sustained (without variation) when the ambient temperature varies, e.g., with precision parts of, for example, a torque indicator and time-measuring spring; precision structures involved in, e.g., precision bellows, an absolute manometer, a flow meter, an industrial manometer and Bourdon's tube; and vibrators included in, e.g., a tuning fork and oscillator.
Hitherto, an Fe-Ni alloy (elinvar) has been widely accepted as the CME alloy. However, this type of CME alloy has certain drawbacks, in that said alloy has to be applied in the cold worked form, and the conditions of cold working have adversely affected the CME properties and mechanical features, thereby obstructing the practical application of such CME alloy.
Therefore, there has been a recent trend toward the application of a precipitation hardening type CME alloy of Fe-Ni-Cr-Ti-Al. If the cold working conditions and heat treating conditions are properly selected, this precipitation type CME alloy can have its thermal elasticity coefficient (abbreviated as "TEC") easily reduced to zero, or to a value approximating zero. Further, said precipitation type CME alloy has great mechanical strength.
However, the upper limit of the temperature range within which said precipitation-type CME alloy can sustain its CME characteristics generally stands at from 70.degree. to 80.degree. C. On the whole, the ambient temperature of various sensors used with, e.g., an airplane, automobile or industrial plant sometimes rises above 80.degree. C. Consequently, in the above-mentioned applications, a manometer involving bellows or a diaphragm prepared from such a precipitation-type CME alloy has a certain drawback, in that it fails to carry out reliable pressure detection within the temperature range in which said manometer is applied.